While the term USB modem refers to any type of data/fax/voice modem device which can be connected to a computer using USB, the term more commonly describes a specific portable USB device that looks similar to a USB flash drive and can be as small as 100 x 35 x 23mm in physical size and weigh only around 25grams.
These small portable USB fax modems do not require a power source and can be plugged into any USB port on your PC, notebook, or Macintosh computer and can also be disconnected from the computer without turning off the system. One end of the portable USB modem will have a USB interface, while the other end will have an RJ-11port for connecting your phone line.
